This invention a continuation-in-part application of U.S. Pat. application Ser. No. 200,964, filed June 1, 1988, U.S. Pat. No. 4,863,163.
The present invention relates to a vertical jump exercise apparatus for training and conditioning participants in sports activities that call for highly developed jumping abilities. People with the higher vertical jump capability often have a competitive edge in such sports as volleyball, basketball, track, and football. The invention also has utility in training and conditioning for jump recovery for sports such as water and snow skiing.
Leg training and conditioning have long been recognized as desirable, and various proposals have been advanced. Some devices, such as that disclosed in Hartzell U.S. Pat. No. 4,371,162, dated Feb. 1, 1983, for squatting exercises, are unsuited for jumping. In jump training, one approach, (such as disclosed in the advertisement for a "Russian Leaper" in Volleyball Monthly, October 1987, p. 59) utilizes short elastic cords attached to the top of a platform, but provides, in contrast to the present invention, no resistive force in the squatted position, no means to monitor symmetrical equivalence of elastic cord tensions for jumper safety, and no means to adjust resistive forces without disassembling the apparatus.
Training devices embodying a relatively constant resistive force, but without means to track cord movement, are disclosed in the Huber U.S. Pat. No. 3,561,758, dated Feb. 9, 1971, and the Schollmeyer U.S. Pat. No. 3,687,450, dated Aug. 29, 1972. Such devices make no provision for reducing friction at the points at which the cords emerge from the apparatus en route to attach to the user. The cords of these devices will inherently rub against the nonmoving surfaces from which they emerge and create a destructive and undesired frictional force.
Other training devices embodying a relatively constant resistive force with track cord movement are disclosed, e.g., in the Zinkin U.S. Pat. No. 4,685,670, dated Aug. 11, 1987. Such devices are only capable of transmitting forces in a one-dimensional plane. Thus, the entire device embodying all moving parts, force elements, and restraining devices must rotate with the user to track movement. This requires a user of his device to provide a generally nontransportable means of support such as a doorway, or roof. Moreover, the rigid bodies restraining force elements of such devices must be physically displaced or reconfigured to adjust tension.
Vertical jump conditioning and training is accomplished by strengthening leg muscles and increasing the speed of the motor reflexes of the legs.
Leg muscles are strengthened by simulating an increase in body weight at or near the user's center of gravity during jump training. Leg strengthening is accomplished in the present invention by providing a waist band with elastic cords attached to a base. The user jumps against the resistive force of the elastic cords, simulating an increase in weight. The resistive force is adjustable to fit the needs of the user.
Motor reflexes of the legs cannot be maintained if a person increases his leg strength performing slow-motion exercises with weights, such as squats or leg presses. When a person loses the ability to jump quickly from the squatting position to the extended leg position, he loses the ability to gain the inertia to propel him into the air after the feet leave the ground. This can result in a lower vertical jump even after an increase of leg strength is acquired.
To maintain quick motor reflexes while increasing one's leg strength for jumping purposes, a person must perform the leg exercises at speeds near his natural jumping speed. This can only be accomplished if the device attached to the user does not have a large mass with inherent inertia which will resist acceleration. A person using conventional exercise devices with free weight cannot move at natural speeds because he must deal with the inherent inertia of the motionless weight being used. It takes much more energy to start and stop 100 pounds of dead weight at jumping speeds than a couple of ounces of shockcord which can provide the same 100 pounds of resistance through the same range of motion. The present invention allows the jumping exercise to be performed at near natural speeds because the source of resistance only weighs ounces. Thus, the unbalancing and dangerous forces of inertia created by accelerating dead weight to jumping speeds are virtually eliminated.
The present invention provides nearly constant resistive force throughout the range of the jump. In other words, from the minimum squatting height of any user to the fully extended leg position of the jump, the simulated weight increase is nearly constant. Without this feature, the force exerted on the jumper in the squatting position of the jump would be far less than the force applied at the point where the jumper's feet are extended and about to leave the ground. This causes the user to miss the benefits of exercising the legs in the squatting position of the jump where humans have a mechanical disadvantage against accelerating upward. Users of this type of device, such as the referenced "Russian Leaper", also incur an unpleasant and potentially harmful snap-back midway through the upward motion of the jump where slack in the elastic cord is finally reduced to zero.
During repetitive jumping exercises, a jumper may move from the center of the exercise area, and it is therefore desirable that a jump exercise device provide forces tending to restore the jumper to the center of the exercise area. Such centering forces should not be so strong as to pull an off-center jumper off balance. The present invention may provide an adjustable centering force that may gradually move the jumper back to the center of the area.
In the preferred embodiment, the present invention employs elastic cords attached to a waist band on the user and to a platform forming an exercise area. The effective length of the cords is increased by directing the cords beneath the platform and routing them through a series of pulleys. A tracking device that directs each cord from the exercise area to beneath the platform includes pulleys and a movable frame to decrease friction and to follow off-center motion of the cord. The frame may be mounted on a pivot for arcuate motion or on a rail for linear motion. The movable frame is particularly important in a jump exerciser because of uncertain directional control of the jumper that may tend to derail the cord.
Accordingly, it is an object of the present invention to provide a vertical jump exercise apparatus that obviates the problems of the prior art and that is usable in a variety of locations.
It is another object of the present invention to provide a vertical jump exercise apparatus with means to follow rapid and off-center jumps while maintaining the resistive force cords on the guide pulleys.
It is yet another object of the present invention to provide a novel vertical jump exercise apparatus that has a nearly constant resistive force through the full range of any user's jumping motion.
It is a further object of the present invention to provide a vertical jump exercise apparatus with an adjustable resistive force, and one which may be adjusted without reconfiguring the position of any rigid body of the device or interchanging parts.
It is yet a further object of the present invention to provide a vertical jump exercise apparatus with a visual indication when there is a resistive imbalance between any cords, and which provides means for easily correcting any undesired imbalance.
It is yet still a further object of the present invention to provide a vertical jump exercising apparatus in which the user can set the resistance from ground zero of the jumping surface.
It is still a further object of the present invention to provide a vertical jump exercise apparatus with relatively low friction at each point the resistive force cord changes direction, by making all surfaces with which the force element can come in contact freely moving.